Lethal and sublethal effects of selected systemic and contact insecticides on the whitefly predator, Nephaspis oculata (Coleoptera: Coccinellidae), in a tri-trophic system

Authors: TARAVATI, SIAVASH - University Of California; MANNION, CATHERINE - University Of Florida; OSBORNE, LANCE - University Of Florida; McKenzie, Cindy

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2018
Publication Date: 4/30/2019
Citation: Taravati, S., Mannion, C., Osborne, L., McKenzie, C.L. 2019. Lethal and sublethal effects of selected systemic and contact insecticides on the whitefly predator, Nephaspis oculata (Coleoptera: Coccinellidae), in a tri-trophic system. Journal of Economic Entomology. 112(2):543-548. https://doi.org/10.1093/jee/toy364.
DOI: https://doi.org/10.1093/jee/toy364

Interpretive Summary: Nephaspis oculata is a whitefly beetle predator which has been reported feeding on several whitefly species including rugose spiraling whitefly (RSW) in south Florida. The management of RSW has been heavy reliant on the use of insecticides which may negatively impact biological control agents. We studied the effect of bifenthrin (spray) and imidacloprid (drench) application on survival, fecundity, and behavior of Nephaspis oculata in the laboratory. Generally, beetles avoided bifenthrin treatments and did not survive as long as imidacloprid treatments. The results from this study shows that systemic imidacloprid is not repellent to Nephaspis oculata and does not significantly affect mortality of adult beetles in the tri-trophic system tested. Therefore, using systemic imidacloprid and Nephaspis oculata for controlling RSW might be compatible or at least not significantly incompatible. Future studies in the field may help us to have a better understanding about such interactions in the landscape.

Technical Abstract: Nephaspis oculata is a whitefly predator which has been reported feeding on several whitefly species. In south Florida, it attacks rugose spiraling whitefly (RSW), an invasive pest of urban trees which was first reported in the United States in 2009. The management of RSW has been heavy reliant on the use of insecticides which may negatively impact biological control agents. We studied the effect of bifenthrin (spray) and imidacloprid (drench) application on survival, fecundity, and behavior of Nephaspis oculata in the laboratory. Adult beetles survived significantly longer in control and systemic imidacloprid compared to bifenthrin treatments but there was no significant difference between control and systemic imidacloprid applications. There was no significant difference in the survival of males and female beetles. The fecundity of beetles in the imidacloprid treatment was significantly lower than the control. Beetles were seen feeding on both the RSW nymphs and honeydew accumulation on petri-dish lids. There was no significant difference between the survival of beetles on aged (3 months) bifenthrin treated leaves and control. Beetles avoided bifenthrin treated leaves but did not avoid systemic imidacloprid-treated or control leaves in a no-choice test. Also, beetles’ feeding rate on bifenthrin-treated RSW nymphs was significantly lower in a no-choice test. In the choice-test, there was a significant difference in feeding rates on whiteflies between choices in the bifenthrin/control treatment but no significant difference in control/control or in imidacloprid/control treatments. The results from this study shows that systemic imidacloprid is not repellent to Nephaspis oculata and does not significantly affect mortality of adult beetles in the tri-trophic system tested. Therefore, using systemic imidacloprid and Nephaspis oculata for controlling RSW might be compatible or at least not significantly incompatible. Future studies in the field may help us to have a better understanding about such interactions in the landscape.